U.S. patent application number 11/531466 was filed with the patent office on 2008-03-13 for regeneration control system for a particulate filter.
Invention is credited to Frank Ament, David B. Brown.
Application Number | 20080060350 11/531466 |
Document ID | / |
Family ID | 39154825 |
Filed Date | 2008-03-13 |
United States Patent
Application |
20080060350 |
Kind Code |
A1 |
Ament; Frank ; et
al. |
March 13, 2008 |
REGENERATION CONTROL SYSTEM FOR A PARTICULATE FILTER
Abstract
A regeneration control system for a particulate filter (PF)
includes a condition module and an oxygen-level module. The
condition module determines whether an oxygen limiting event is
required for the PF during a regeneration event. The oxygen-level
control module communicates with the condition module and
selectively limits an oxygen level in the PF during the
regeneration event.
Inventors: |
Ament; Frank; (Troy, MI)
; Brown; David B.; (Brighton, MI) |
Correspondence
Address: |
GENERAL MOTORS CORPORATION;LEGAL STAFF
MAIL CODE 482-C23-B21, P O BOX 300
DETROIT
MI
48265-3000
US
|
Family ID: |
39154825 |
Appl. No.: |
11/531466 |
Filed: |
September 13, 2006 |
Current U.S.
Class: |
60/295 ; 60/278;
60/280; 60/297 |
Current CPC
Class: |
F01N 13/009 20140601;
F02D 41/029 20130101; F02D 2200/0812 20130101; F02D 41/1446
20130101; Y02T 10/47 20130101; F01N 2560/06 20130101; F02M 26/05
20160201; F02D 2250/14 20130101; F01N 9/002 20130101; F01N 13/107
20130101; F01N 3/103 20130101; F02D 41/18 20130101; Y02T 10/40
20130101; F02B 37/22 20130101; F01N 2560/025 20130101; F02B 1/12
20130101; F02B 3/06 20130101 |
Class at
Publication: |
60/295 ; 60/278;
60/280; 60/297 |
International
Class: |
F02M 25/06 20060101
F02M025/06; F01N 5/04 20060101 F01N005/04; F01N 3/00 20060101
F01N003/00 |
Claims
1. A regeneration control system for a particulate filter (PF)
comprising: a mass air flow (MAF) sensor that generates a MAF
signal; a condition module that determines whether an oxygen
limiting event is required for the PF during a regeneration event
based on said MAF signal; and an oxygen-level module that
communicates with said condition module and selectively limits an
oxygen level in the PF during said regeneration event, wherein said
condition module determines a maximum oxygen content level based on
said MAF signal and generates an air flow reduction signal when a
current oxygen content level is greater that said maximum oxygen
content level.
2. The regeneration control system of claim 1 wherein said
condition module determines whether said oxygen limiting event is
required based on at least one of an oxygen level signal, a
temperature signal.
3. The regeneration control system of claim 2 wherein said
condition module determines that said oxygen limiting event is
required when said oxygen level signal exceeds an oxygen level
threshold.
4. The regeneration control system of claim 3 wherein said
condition module determines that said oxygen limiting event is
required when said temperature signal exceeds a temperature
threshold.
5. The regeneration control system of claim 4 wherein said
condition module determines that said oxygen limiting event is
required when said airflow signal does not exceed an airflow
threshold.
6. The regeneration control system of claim 2 wherein said
oxygen-level control module limits said oxygen level in the PF when
said condition module determines that said oxygen limiting event is
required.
7. The regeneration control system of claim 6 wherein said
oxygen-level control module limits said oxygen level in the PF with
at least one of an exhaust gas recirculation valve, a variable
nozzle turbine turbo, and a throttle.
8. The regeneration control system of claim 7 further comprising a
timer that starts timing when said condition module determines that
said oxygen limiting event is required and that generates a disable
signal after a predetermined period.
9. The regeneration control system of claim 8 wherein said
condition module determines that said oxygen limiting event is not
required when said disable signal is generated.
10. The regeneration control system of claim 8 wherein said
oxygen-level control module does not limit said oxygen level in the
PF when said disable signal is generated.
11. A method to reduce temperature in a particulate filter (PF),
comprising: generating an airflow signal; determining whether an
oxygen limiting event is required for the PF during a regeneration
event; selectively limiting an oxygen level of the PF during said
regeneration event; determining that said oxygen limiting event is
required when said airflow signal does not exceed an airflow
threshold.
12. The method of claim 11 further comprising determining whether
said oxygen limiting event is required based on at least one of an
oxygen level, a temperature, and an airflow.
13. The method at claim 12 further comprising determining that said
oxygen limiting event is required when said oxygen level exceeds an
oxygen level threshold.
14. The method of claim 13 further comprising determining that said
oxygen limiting event is required when said temperature exceeds a
temperature threshold.
15. The method of claim 14 further comprising determining that said
oxygen limiting event is required when said airflow does not exceed
an airflow threshold.
16. The method of claim 12 further comprising limiting said oxygen
level in the PF when said oxygen limiting event is required.
17. The method of claim 16 further comprising limiting said oxygen
level in the PF with at least one of an exhaust gas recirculation
valves a variable nozzle turbine turbo, and a throttle.
18. The method of claim 17 further comprising limiting said oxygen
level for a predetermined period.
19. The regeneration control system of claim 1 wherein said
oxygen-level module generates a control signal based on said air
flow reduction signal to adjust at least one of a throttle, an
exhaust gas recirculation valve and a turbine turbo.
20. The method of claim 11 comprising adjusting a cross-sectional
area of said inlet.
21. (canceled)
22. A regeneration control system for a particulate filter (PF)
comprising: a condition module that determines whether an oxygen
limiting event is required for the PF during a regeneration event;
an oxygen-level module that communicates with said condition module
and selectively limits an oxygen level in the PD during said
regeneration event; and a timer that starts timing when said
condition module determines that said oxygen limiting event is
required and that generates a disable signal after a predetermined
period to limit oxygen limiting time.
23. The regeneration control system of claim 22 wherein said
predetermined period is independent of state particulate
regeneration.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to vehicle exhaust systems,
and more particularly to particulate filters in vehicle exhaust
systems.
BACKGROUND OF THE INVENTION
[0002] During combustion in a diesel engine, an air/fuel mixture is
compressed within a cylinder. Heat generated from compression
ignites the air/fuel mixture expanding gases within the cylinder to
drive a piston. Exhaust gases are released from the cylinder into
an exhaust system.
[0003] A diesel particulate filter (DPF) disposed in the exhaust
stream filters soot particulates in the exhaust gas. Over time the
soot particulates build up inside the DPF. The DPF is periodically
cleaned using a regeneration technique that burns the soot
particulates.
[0004] One conventional regeneration method injects diesel fuel
into the cylinder after combustion. Post-combustion injected fuel
is expelled from the cylinders with the exhaust gas and is oxidized
over catalysts. Heat released during oxidation increases the
exhaust gas temperature, which burns trapped soot particulates in
the DPF. However, in some circumstances regeneration may generate
temperatures that are high enough to damage the DPF causing thermal
stress and/or melting,
[0005] Various approaches have been employed to limit peak
temperatures within the DPF. In one approach, post-combustion
injected fuel is limited. However, this approach is ineffective
because buildup of soot particulates in the DPF may be sufficient
to create an exothermic reaction that increases the
temperature.
[0006] In another approach, regeneration is performed more
frequently to limit the buildup of soot particulates. However, if a
vehicle has short driving cycles, the temperature of the exhaust
gases may not be high enough to burn the soot particulates, Thus,
regeneration may not occur when needed and soot particulates may
build up in the DPF.
SUMMARY OF THE INVENTION
[0007] A regeneration control system for a particulate filter (PF)
according to the present invention includes a condition module and
an oxygen-level module. The condition module determines whether an
oxygen limiting event is required for the PF during a regeneration
event. The oxygen-level control module communicates with the
condition module and selectively limits an oxygen level in the PF
during the regeneration event.
[0008] In other features, the condition module determines whether
the oxygen limiting event is required based on an oxygen level
signal, a temperature signals and/or an airflow signal. The
condition module determines that the oxygen limiting event is
required when the oxygen level signal exceeds an oxygen level
threshold. The condition module determines that the oxygen limiting
event is required when the temperature signal exceeds a temperature
threshold. The condition module determines that the oxygen limiting
event is required when the airflow signal does not exceed an
airflow threshold.
[0009] In still other features, the oxygen-level control module
limits the oxygen level in the PF when the condition module
determines that the oxygen limiting event is required. The
oxygen-level control module limits the oxygen level in the PF with
an exhaust gas recirculation valve, a variable nozzle turbine
turbo, and/or a throttle.
[0010] In yet other features, the regeneration control system
includes a timer that starts timing when the condition module
determines that the oxygen limiting event is required and generates
a disables signal after a predetermined period. The condition
module determines that the oxygen limiting event is not required
when said disable signal is generated. The oxygen-level control
module does not limit the oxygen level in the PF when the disable
signal is generated.
[0011] Further areas of applicability of the present invention will
become apparent from the detailed description provided hereinafter.
It should be understood that the detailed description and specific
examples, while indicating the preferred embodiment of the
invention, are intended for purposes of illustration only and are
not intended to limit the scope of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] The present invention will become more fully understood from
the detailed description and the accompanying drawings,
wherein:
[0013] FIG. 1 is a functional block diagram of a diesel engine
system using a regeneration control system according to the present
invention;
[0014] FIG. 2 is a functional block diagram of the regeneration
control system according to the present invention;
[0015] FIG. 3 is an exemplary table that may be used to determine a
maximum exhaust oxygen content; and
[0016] FIG. 4 is a flowchart illustrating exemplary steps taken by
the regeneration control system to limit oxygen in the diesel
engine system.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0017] The following description of the preferred embodiment(s) is
merely exemplary in nature and is in no way intended to limit the
invention, its application, or uses. As used herein, the term
module or device refers to an application specific integrated
circuit (ASIC), an electronic circuit, a processor (shared,
dedicated, or group) and memory that executes one or more software
or firmware programs, a combinational logic circuit, and/or other
suitable components that provide the described functionality.
[0018] According to the present invention, oxygen levels in exhaust
gases may be limited to reduce temperatures during regeneration in
a particulate filter (PF). When oxygen levels are reduced in the
exhaust gases there is less soot oxidation, which limits the
temperature within the PF.
[0019] Referring now to FIG. 1, an exemplary diesel engine system
10 is illustrated. It is appreciated that the diesel engine system
10 is merely exemplary in nature and that regeneration system
described here in can be implemented in various engine systems
implementing a particulate filter. Such engine systems may include,
but are not limited to, gasoline direct injection engine systems,
compressed natural gas engine systems, and homogeneous charge
compression ignition engine systems. For ease of the discussion,
the disclosure will be discussed in the context of a diesel engine
system.
[0020] The diesel engine system 10 includes an engine 12, an intake
manifold 14, a fuel injection system 16, and an exhaust system 18.
The exemplary engine 12 includes six cylinders 20 configured in
adjacent cylinder banks 21,22 in a V-type layout. Although FIG. 1
depicts six cylinders (N=6), it can be appreciated that the engine
12 may include additional or fewer cylinders 20. For example,
engines having 2, 3, 4, 5, 6, 8, 10, 12 and 16 cylinders are
contemplated. It is also appreciated that the present invention may
be used in accordance with an inline-type cylinder configuration or
any other type of configuration known in the art.
[0021] The diesel engine system 10 may include a variable nozzle
turbine (VNT) turbo 23 that pumps additional air into the intake
manifold 14 for combustion. A throttle 25 may be adjusted to
control air flow through the intake manifold 14 and into the
cylinders 20 from the intake manifold 14. Fuel is injected into the
cylinders 20 with the fuel injection system 16. Heat generated from
compressed air ignites the air/fuel mixture. The exhaust gases exit
the cylinders 20 to the exhaust system 18.
[0022] The exhaust system 18 includes exhaust manifolds 29 and 30,
exhaust conduits 33 and 34, a diesel oxidation catalyst (DOC) 31,
and a diesel particulate filter (DPF) 32. Exhaust manifolds 29,30
direct the exhaust gases from corresponding cylinder banks 21,22
into exhaust conduits 33,34. The exhaust conduits 33,34 lead to an
inlet 35 of the VNT turbo 23.
[0023] The flow of exhaust gases through the VNT turbo 23 generates
power in the VNT turbo 23 sufficient to compress additional air
into the intake manifold 14. The power generated may be varied by
adjusting a cross sectional area of the inlet 35 controlling the
rate of exhaust flow through the VNT turbo 23 and into the DOC 31.
The DOC 31 oxidizes unburned hydrocarbons in the exhaust gases over
a catalyst. Heat that is released during oxidation of the
hydrocarbons increases the temperature of the exhaust gases. The
heated exhaust gases burn soot particulates trapped in the DPF
32.
[0024] An exhaust gas recirculation system includes a recirculation
conduit 36 and an exhaust gas recirculation (EGR) valve 37. The EGR
valve 37 recirculates exhaust gases into the intake manifold 14.
The EGR valve 37 may be modulated between open and closed positions
to allow a partial flow of exhaust gases.
[0025] A regeneration control system 42 regulates operation of the
diesel engine system 10. A mass air flow (MAF) sensor 44 is
responsive to mass air flow and generates a MAF signal 46 based
thereon. A temperature sensor 48 is responsive to the temperature
of exhaust gases from the DOC 31 and generates a temperature signal
50 based thereon. An oxygen sensor 52 is responsive to a
concentration of oxygen in the exhaust gases from the DOC 31 and
generates an exhaust oxygen-level signal 54 based thereon. The
regeneration control system 42 receives the temperature signal 50
and the exhaust oxygen-level signal 54 and generates a control
signal based thereon. Alternatively, the control signal may be
based on the MAF signal 46, the temperature signal 50, and the
exhaust oxygen-level sensor 54.
[0026] Referring now to FIG. 2, a functional block diagram 70
illustrates the regeneration control system 42 in further detail.
The regeneration control system 42 may include a condition module
74 and an oxygen-level control module 76. The condition module 74
selectively generates an air flow reduction signal 80 based on the
MAF signal 46, the temperature signal 50, and the exhaust
oxygen-level signal 54. More specifically, the condition module 74
determines a maximum exhaust oxygen content based on a total
exhaust flow rate of the exhaust system 18, whether the temperature
signal 50 is greater than a temperature threshold, and whether the
exhaust oxygen-level signal 54 is greater than the maximum
determined oxygen-level threshold. In a preferred embodiment the
maximum oxygen content is determined from the MAF, which varies
from 2 to 21%, and the temperature threshold is 500.degree. C. An
exemplary table that may be used to determine the maximum exhaust
oxygen content based on the total exhaust flow rate of the exhaust
system 18 is depicted in FIG. 3. If the exhaust oxygen content is
greater than the maximum value based on the MAF signal and the
temperature signal 50 is greater than the temperature threshold,
the condition module 74 generates the air flow reduction signal 80.
The oxygen-level control module 76 generates a control signal 82
when the airflow reduction signal 80 is received. The control
signal 82 is based on the oxygen-level signal 54 and may be used to
control the EGR valve 37, the VNT turbo 23, and/or the throttle 25
and consequently control the oxygen level of the DPF 32.
[0027] The engine system 10 may not be operating in a preferred
mode when the oxygen level is limited by the regeneration control
system 42. Thus, the oxygen level is only limited for a
predetermined period. A timer 84 is set at the beginning of a
regeneration event to track an elapsed time. The timer generates a
disable signal 86 that is received by the condition module 74 when
the elapsed time exceeds the predetermined period. It may be
appreciated by those skilled in the art that other elements capable
of comprehending a particulate oxidation status may be used in
place of the timer 84 to determine when to stop limiting the oxygen
level. The other elements can be empirically based and/or models
capable of estimating when conditions for oxygen limitation are no
longer needed. When the condition module 74 receives the disable
signal 86, the airflow reduction signal 80 is no longer generated
and the oxygen-level control module 76 does not limit the oxygen
level.
[0028] Referring now to FIG. 4, a flowchart illustrating exemplary
steps taken by the regeneration control system 42 are generally
identified at 100. Control starts in step 101 when the diesel
engine system 10 is started. In step 102, control determines
whether regeneration is activated. If regeneration has not been
activated, control ends in step 103. If regeneration has been
activated, the condition module 74 determines whether the
temperature signal 50 (T) is greater than the temperature threshold
(T.sub.THR) in step 104. If the temperature signal 50 is not
greater than the temperature threshold, control ends in step
103.
[0029] In step 105 control starts the timer 84. The condition
module 74 measures the MAF in step 106 and then determines the
maximum exhaust content based on the MAF in step 107. In step 108,
control compares the oxygen-level signal 54 (O.sub.2) to the oxygen
threshold (O.sub.2THR) determined in step 107 to determine whether
the oxygen level in the exhaust gas is too high. If O.sub.2 is
greater than O.sub.2THR control proceeds to step 110. In step 110,
the oxygen level in the exhaust gases is reduced. More
specifically, the oxygen level is reduced by increasing EGR with
the EGR valve 37, adjusting the inlet 35 of the VNT turbo 23,
and/or adjusting the throttle 25. If O.sub.2 is not greater than
O.sub.2THR control proceeds to step 112.
[0030] In step 112 control determines whether the timer 84 has
expired. If the timer 84 has expired, control generates the disable
signal 86 to disable the condition module 74 in step 114 and
control ends in step 103. If the timer 84 has not expired, control
returns to step 106.
[0031] Those skilled in the art can now appreciate from the
foregoing description that the broad teachings of the present
invention can be implemented in a variety of forms. Therefore,
while this invention has been described in connection with
particular examples thereof, the true scope of the invention should
not be so limited since other modifications will become apparent to
the skilled practitioner upon a study of the drawings,
specification, and the following claims.
* * * * *